Since the establishment of the United States in 1776, numerous state partition proposals have been put forward that would either set-off a portion of an existing state (or states) in order that this region might either join another state or create a new state. Article IV, Section 3, Clause 1 of the United States Constitution, oftentimes called the New States Clause, grants to the United States Congress the authority to admit new states into the United States beyond the thirteen already in existence at the time the Constitution went into effect (June 21, 1788, after ratification by nine of the thirteen states[1]):

New States may be admitted by the Congress into this Union; but no new State shall be formed or erected within the Jurisdiction of any other State; nor any State be formed by the Junction of two or more States, or Parts of States, without the Consent of the Legislatures of the States concerned as well as of the Congress.[2]

Four Eastern states had Western land claims when the Constitution was written. The New States Clause was designed to give them a veto over whether their western counties could become states.[3] The clause has served this same function since then whenever a proposal to partition an existing state or states has come before Congress. New breakaway states are permitted to join the Union, but only with the proper consents.[4] Of the 37 states admitted to the Union by Congress, Kentucky, Maine, and West Virginia were each set off from an already existing state:

The following is a list of substantive proposals (both successful and unsuccessful) put forward since the nation's founding to partition or set-off a portion of an existing U.S. state (or states) in order that the region might either join another state or create a new state. Proposals to secede from the Union are not included, nor are proposals to create states from either organized incorporated or unorganized U.S. territories. Land cessions made by several individual states to the Federal government during the 18th and 19th centuries are not listed either.

In February 2011, Tucson politicians and activists formed the group "Start our State," to advocate secession for Pima County and other southern counties to create a state called "Baja Arizona". The group wanted the Pima County Board of Supervisors to put the issue on the 2012 ballot, but it was rejected by the Board due to lack of authority, so the group circulated petitions.[6] Interest in secession grew when Republican Governor Jan Brewer and her allies enacted Arizona SB 1070, regarding illegal immigration.[7] Furthermore, the state had passed laws affecting Tucson elections and how the city bids for public works projects.[8]

2013 election results: counties in orange voted to separate from Colorado, while counties in blue rejected the idea.

In the mid-1930s, the Walsenburg World-Independent proposed that Huerfano County secede from the state.[9] This was a pet project of Sam T. Taylor, a sports editor, who went on to become a long-serving state senator,[10] continuing to pursue the idea unsuccessfully.[11]

In 1973, nearby Costilla County had expressed interest in seceding from Colorado and joining New Mexico.[12]

On June 6, 2013, commissioners in Weld County announced a proposal to secede with seven other counties to form the state of North Colorado, citing concerns with state policy and recently enacted legislation relating to the region’s main economic drivers, including agriculture and energy. The bid was motivated by a belief that the urban population centers of the State weren't concerned with the economic interests of more rural areas.[13][14][15] The commissioners stated that they would hold public meetings to gather input before crafting a ballot initiative by August 1, and that the proposal had aroused preliminary interest from fellow commissioners in Morgan, Logan, Sedgwick, Phillips, Washington, Yuma and Kit Carson counties.[16] Eleven counties were involved in the partition movement by election day, though Moffat County was looking into joining Wyoming rather than North Colorado.[17] Voters rejected partition in six of the eleven counties, including Weld and Moffat, and supported it (without binding authority) in five.[18]

Between 1840 and 1842, several northern counties in Illinois, including Jo Daviess County, Stephenson County, Winnebago County and Boone County, voted to reattach to Wisconsin, from which the counties were ceded to Illinois by Congress in 1818. The split was precipitated by the mutual antagonism between northerners and southerners due to social and political differences. The split was never realized due to lack of support from Chicago and Cook County, as the benefits of the Illinois and Michigan Canal linking northern to central and southern Illinois outweighed secession.[21]

In 1925, Cook County considered secession to create the state of Chicago.[24]

In the early 1970s, residents in western Illinois were upset over the allocation of state funds for transportation, prompting a student at Western Illinois University to declare 16 counties the Republic of Forgottonia. Although the declaration was meant to be a joke, the secession idea was picked up by the Western Illinois Regional Council, until State Representative Doug Kane showed that the counties had received funding that was more than what they paid in state taxes.[25]

In November 2011, State Representatives Bill Mitchell and Adam Brown introduced a proposal to make Cook County a state of its own. They felt that all of Illinois outside of Cook County should become a separate state, due to Chicago's "dictating its views" to the rest of the state.[26]

In 1992, a group in southwestern Kansas advocated the secession of a number of counties in that region from the state. Nominally headed by Don O. Concannon, a lawyer and former gubernatorial candidate from Hugoton, the group called the new state name "West Kansas", a state bird (pheasant), and a state flower (yucca). The proposal was in reaction to laws raising real estate taxes, and shifting state education funding away from rural school districts and into more urban areas. Though organizers arranged for a series of straw polls that demonstrated widespread support for secession in nine counties,[27] the movement died out by the mid-1990s.[28]

Maine was initially part of the Commonwealth of Massachusetts before being admitted to the Union as a state in 1820. However, its boundary with British North America (now Canada) had been in dispute for several decades. In 1827, John Baker unilaterally declared the disputed territory (now part of Aroostook County) to be the "Republic of Madawaska". The declaration was rejected by Maine in 1831. Following the undeclared Aroostook War in 1838–1839, the United States and United Kingdom signed the Webster–Ashburton Treaty on August 9, 1842 to settle the border issue.

In 1998 and again in 2005, state representative Henry Joy proposed legislation to partition Maine into northern and southern states. He cited concern for the rural northern part, encompassing Maine's 2nd congressional district, being affected by "anti-business policies" and "overzealous environmental safeguards".[29] Reflecting his political opinion of the trends there, Joy suggested the southern half be named "Northern Massachusetts" and the northern half remain "Maine", though others have suggested "Acadia" for the northern half.[30]

In September 2009, Frederick County Commissioner John L. Thompson Jr. proposed that the county secede from Maryland because the county pays more to state government in taxes than it receives in services and benefits. The proposal was rejected by the other commissioners in the county.[34]

In February 2014, it was reported that residents from Western Maryland started petitions to form a new state, citing taxes and gun control as issues. Possible names for such a proposed state included Liberty, Antietam, and Augusta.[35]

The state's exclaveDistrict of Maine had proposed secession multiple times in the early 19th century. Long-standing disagreements over land speculation and settlements led Maine residents and their allies in Massachusetts proper to force an 1807 vote in the Massachusetts General Court on permitting Maine to separate; the vote failed. Separatist sentiment in Maine was stoked during the War of 1812 when pro-British Massachusetts merchants opposed the war, and refused to defend Maine from British invaders. Finally, on June 19, 1819, the Massachusetts General Court passed enabling legislation separating the "District of Maine" from the rest of the state (an action approved by the voters in Maine on July 19, 1819 by 17,001 to 7,132). Then, on February 25, 1820, the court passed a follow-up measure officially accepting the fact of Maine's imminent statehood.[36] Maine became the 23rd state on March 15, 1820, as part of the Missouri Compromise, which also geographically limited the spread of slavery and enabled the admission to statehood of Missouri the following year.[37][38][39]

Boston Corner, in the southwestern corner of the state, was ceded to the state of New York in 1857, due to Massachusetts being unable to administer the hamlet.

A 1919 tax-protest proposal filed in the state legislature would have created an independent State of Boston.[30]

In 1977, the islands of Martha's Vineyard, Nantucket, and the Elizabeth Islands proposed to separate from Massachusetts because of a redistricting bill that would have deprived Dukes County, consisting of Martha's Vineyard and the Elizabeth Islands, and Nantucket County of separate representation in the General Court. At local town meetings, culminating in the All-Island Selectmen’s Association Conference, residents and community leaders voted in favor of secession with an "overwhelming majority". When the Nantucket state representative filed a bill with the Massachusetts Legislature, Grasso the Governor of Connecticut suggested that the islands join her state, the New Hampshire House of Representatives and the Rhode Island Senate each passed resolutions inviting the islands to join their states, and the Governor of Vermont and the Vermont General Assembly both supported annexation to their state. Although the redistricting bill passed, the state representatives pledged to assign aides for the two counties that would report to their state representative, and the area received much positive publicity.[41][42]

There has been intermittent advocacy for the Arrowhead of Minnesota, the three northeast counties of the state adjacent to Lake Superior, to join with northwestern Wisconsin and the Upper Peninsula of Michigan to form a new state to be named "North Country" or Superior, with Duluth as its capital.[44][45]

In the 1990s, Randy Kuhl, from rural upstate Hammondsport, had advocated secession by regularly proposing bills to that effect while he was a state senator. His 1999 bill would have New York City, Long Island, Westchester and Rockland Counties become a separate state of New York, while the rest of the counties would be grouped as West New York.[58]

From 2007 to 2009, Long Island residents discussed secession on the grounds that their tax money is not used to fund programs in their counties.[59] Proposals were made for the entire island (Kings, Queens, Nassau, and Suffolk counties) and for just the two suburban counties (Nassau and Suffolk).[60][61][62][63][64]

2010 gubernatorial candidate Carl Paladino's supporters, Rus Thompson and James Ostrowski in the Buffalo region, have supported secession of western New York from New York City and its nearby counties.[67]Fred Smerlas, in discussing a potential platform for a 2010 Congressional run from western New York, stated that he would make the separation of New York City and upstate a top priority: "My first act if I ever got elected would be to take a big saw and cut New York City off."[68]

Fifteen towns in the Southern Tier of New York proposed potential secession in 2015.[69]

In 1984, the township of New Shoreham, located on Block Island, threatened to secede because the state had denied them the ability to ban or to control the use of mopeds on the island. Both Massachusetts and Connecticut were reported as having interest in annexing the island. After the town voted to put the issue on the state ballot for June, the Rhode Island government eventually compromised by allowing the island to control the number of mopeds on the island.[72][73]

In 1861, after Tennessee joined the Confederacy, Scott County passed a proclamation to secede from Tennessee and form the "Free and Independent State of Scott" in order to support the Union. When it was discovered in 1986 that this county law was still on the books, the proclamation was finally repealed. The county then petitioned the state of Tennessee for readmission, even though the original secession had not been recognized by the either the state or federal government.[74]

Under the joint resolution of Congress, the Republic of Texas joined the Union with the right to partition itself into as many as five states. As a result, Texas "divisionists" would occasionally propose partitioning in its early decades.[75][76]

State of Deseret, partly settled by Mormons before it was purchased from Mexico by the United States, had proposed boundaries far larger than the eventual Utah Territory.

In 2002, the United States House of Representatives voted to allow Wendover to leave the state and join Nevada, merging with the city of West Wendover.[77][78] However, Nevada Senator Harry Reid blocked the bill's consideration in the Senate, citing that it would affect the investments of the casinos in the border town.[79]

In 2008, state representative Neal Hendrickson proposed Joint Resolution 6 (HJR006): "the creation of a separate state, consisting of the southern portion of the present state of Utah with a northern boundary stretching east and west across the present state of Utah at the southern border of Utah County".[80] The bill did not pass.[81]

The District of Kentucky: Fayette, Jefferson, and Lincoln (all formerly part of Kentucky County) sought on numerous occasions to split from Virginia, beginning in the 1780s. Ten constitutional conventions were held in the Constitution Square Courthouse in Danville between 1784 and 1792. In 1790, Kentucky's delegates accepted Virginia's terms of separation, and a state constitution was drafted at the final convention in April 1792. The Virginia General Assembly adopted legislation on December 18, 1789 separating its "District of Kentucky" from the rest of the State and approving its statehood.[36] Kentucky became the 15th state in the Union on June 1, 1792.[82]

West Virginia: Several Trans–Allegheny region counties voted to secede from the state after Virginia joined the Confederate States of America at the beginning of the Civil War on April 17, 1861. Unionist leaders in Wheeling set up a new State government for Virginia under the Wheeling Convention that was recognized by Washington. On May 13, 1862, the General Assembly of the Restored Government of Virginia passed an act granting permission for creation of West Virginia,[83] and the secessionist area wrote a constitution. It was admitted to the Union as West Virginia[84] on June 20, 1863, the 35th state.[85] Support for the Confederacy and the Union was about evenly divided in the new State and a guerrilla war lasted until 1865.[86] Later, by its ruling in Virginia v. West Virginia (1871), the Supreme Court implicitly affirmed that the breakaway Virginia counties did have the proper consents necessary to become a separate state.[87]

In 2004 and 2005, the town of Killington voted to secede from Vermont to join New Hampshire, despite being situated in the center of the state.[88] A similar motion was attempted in Winhall, but was voted down.[89]

Present-day Washington is geographically divided into Eastern and Western regions by the Cascade Mountains. In the original proposal to establish Washington Territory, it was bounded on the east by the Columbia River.[90] Since 1861, some eastern residents have proposed forming a new state, sometimes in combination with the Idaho Panhandle and relatively small parts of Montana and Oregon (consisting of the greater market area of Spokane). Names proposed include East Washington, Lincoln, and Cascadia. Reasons given are the distinct needs of urban and rural populations and political differences over water rights, labor law, and taxation.[91][92]

Since the 2016 presidential election a proposal has been filed to split into two states : Washington and Liberty.[93]

On July 21, 1967, the Village of Winneconne seceded to become the Sovereign State of Winneconne in order to protest its omission from the state's highway map. After negotiations restored the village's location, Winneconne rejoined the state.[94] The village has since celebrated the secession with an annual Sovereign State Days event.[95]

Portions of the northern counties were included in proposals for the State of Superior.